The Changing Patterns of Infectious Diseases in South Asia:

A Personal Journey

Richard A. Cash, MD, MPH

Harvard School of Public Health

9 September 2013

Outline—IDs That Are……

• Eradicated, eliminated, or controlled

• Deceasing in incidence and severity

• Continuing high incidence but decreasing mortality

• Linked to long-term consequences

• New or reemerging

Agent

Host

Environment

• Age

• Sex

• Genotype

• Behaviour

• Nutritional status

• Health status

• Infectivity

• Pathogenicity

• Virulence

• Immunogenicity

• Antigenic stability

• Survival

• Weather

• Housing

• Geography

• Occupational setting

• Air quality

• Food

• SE status

• Politics

Factors Influencing Disease Transmission

ID’s Eradicated, Eliminated, or Controlled and Primary Intervention

• Smallpox (vaccine)

• Guinea worm (environment/behavior)

• Polio (vaccine)

• Neonatal tetanus (vaccine)

• Diphtheria (vaccine and treatment)

• Leprosy (treatment)

ID’s Decreasing in Incidence with Significant Reduction in M & M from Disease or Associated Conditions

• Measles (vaccine-esp with 2nd dose)

• Rheumatic fever (treatment and development?)

• Hepatitis B (vaccine)

• Helicobacter pylori and Peptic Ulcers(treatment, H2 blockers)

ID’s with a Higher Incidence but Reductions in Mortality and Morbidity

• Diarrhea (treatment)

• Lower respiratory infection (treatment, vaccines--measles, DP)

• Tuberculosis (?) (treatment)

• Malaria (bed nets and treatment)

ID’s—Long-term Consequences

• Hepatitis B-cancer and chronic hepatitis (vaccine, treatment?)

• Human papilloma virus (HPV)-cervical cancer (screening and vaccine)

• Hepatitis C-cancer and chronic hepatitis (safe injections)

• JE—mental health problems/retardation-(vaccine and environment)

ID’s—New and Reemerging

• HIV/AIDS• SARS• H5N1 “Avian” Flu & H1N1 “Swine” Flu• Nipah• Dengue• Hepatitis C• MDR/XDR TB, malaria and other a drug

resistant organisms

Nipah—Case Definition

• Confirmed case– Fever– Headache or altered level of

consciousness– Positive antibody test (IgM or IgG)

• Probable cases– Consistent symptoms– Epidemiologically linked

Nipah—Risk Factors in Malaysia

• The outbreak was concentrated among pig farmers—(92% of cases reported contact with pigs)

• Compared to controls, persons with Nipah encephalitis were

– 5.6X more contact with pigs.

– 3.7X more contact with sick pigs

Nipah—Outbreak Control in Malaysia

• Outbreak stopped following the culling of over 2 million pigs– Fruit trees were no longer permitted

above pig pens– Pork industry decimated

• No cases of Nipah recognized in people or animals since these measures were taken

How Often do Bats Visit Date Palm Trees?

• Identified tree 500 meters from P. giganteus roost

• Mounted silent infrared wildlife camera

• 49 bats visited the tree– 26 drank sap from

the shaved part of the tree

Photo by Salah Uddin Khan

Zoonoses are Expensive

• BSE—UK 1990-98--$9 Billion

• Plague—India 1995--$1.7 Billion

• Nipah—Malaysia 1998--$540 Million

• SARS—China 2003-->$50 Billion

• Avian flu (H5N1)—Global 1997-2006-- $Billions

Factors Enhancing ID Spread• Increased population density• Inadequate infrastructure especially for

water/sanitation• Movement of people through travel or

social disruption• Centralized food production• Antibiotic and other drug overuse, under

treatment and counterfeit drugs• Ineffective government control

Factors to Reduce the Incidence and Improve the Control of IDs

• Increase and maintain high levels of immunization and introduce new vaccines when cost-effective

• Reduce environmental risks, especially water/sanitation and air pollution

• Improve local and national surveillance and laboratory support• Train and employ more epidemiologists and public health

experts

Reducing Incidence and Improving Control of ID (II)

• Vector control in urban and rural areas• Improve and enforce guidelines for antibiotic

use• Develop an approach to control that is

consistent with local realities• Seek greater global and local equity in the

distribution of vaccines and drug

Factors that Favor the Ability to Limit the Impact of NRE IDs

• Increased knowledge of epidemiology, microbiology, treatment, and behavior and access to information

• Vaccines and drugs

• Better nutrition

• Democratization of pathogens

• Surveillance

Lessons from Quotes and History

• “Chance favors the prepared mind.” Louis Pasteur

• “You cannot step in the same river twice.” Heraclitus

• “Everything should be as simple as possible but not one bit simpler” Albert Einstein